Projectile



July 11, 1961 McG, MILLAR 7 2,991,719

PROJECTILE Filed June 24, 1944 14,, I5 2 I4 14p 12 F161] I3 III) //a parts somewhat loosely.

United States Patent "2,991,719 PROIECTILE John McG. Millar, Utica, N.Y., assignor tothe United States of America as represented by the Secretary of the Navy Filed June 24, 1944, Ser. No. 541,923 3'Claims. (Cl. 10293) initial direction of flight, but being firmly held on the core prior to firing. I

In projectiles which include a subcaliber core and a releasable sabot, a difiiculty frequently encountered is that of holding the parts of the projectile together prior to loading into the gun, without impairing proper release of the sabot after firing. This difliculty has to a degree been dealt with in some cases by assembling the projectile However, in such projectiles, trouble is encountered in-handling the projectiles, as in packing operations at the factory or in the field while unpacking or in loading. Unless particular care is 'observed, the component elements frequently separate. In

the event that the projectile elements do come apart, it

is possible that some of the elements will be lost or damaged. At best, considerable time must be consumed in reassembling the separated elements, and in service use this is a serious disadvantage.

Even where provision is made for positive retention of the projectile parts, a further problem arises in obtaining release of the sabot early in its flight. Where release is made possible by automatic disengagement of some form of positive retaining means, it is obvious that a delicate balance must be established between locking and unlocking, because otherwise the sabot will not be released and the entire purpose of the projectile will be defeated.

Accordingly, a further object of the invention is the provision of a projectile in which a subcaliber core and a sabot are positively held in assembled relationship in such a manner as to overcome the above described difliculties, and are conditioned for separation after the projectile is fired, the conditioning being effected by centrifugal force and/ or setback.

A further object of the invention is the provision of a projectile of the character referred to above which is simple to manufacture and is adapted to large quantity production.

These and other objects of the invention will be apparent from the following specification and the accompanying drawing, in which:

FIG. 1 is a longitudinal sectional view of a preferred form of the invention;

FIG. 2 is a cross-sectional view taken on line 2-2 of FIG. 1;

FIG. 3 is a front elevational view of the projectile shown in FIG. 1;

FIG. 4 is a side elevational view, partly in section, of a modified form of bourrelet for use with the projectile; and

FIG. 5 is a side elevational view of the sabot shown in FIG. 1.

The projectile assembly in the form illustrated includes a substantially cylindrical subcaliber core and a sabot in the form of a cup or base plate fitting about the rear portion of the core and locked to the core by means of a resilient split ring locking element. The ring wedges be- 2,991,719 Patented July 11, 1961 tween adjacent fluted ortapered surfaces of the members to be interlocked, and effects locking by frictional contact and by a wedging action. A clearance is afforded between the tapered surfaces to permit free release of the ring by centrifugal force and/or setback prior to the time complete discard of the sabot is required after firing. Locking and release are achieved without the critical necessity of finishing the tapered surfaces within close tolerance limits.

Referring to FIGS. 1 through 3 of the accompanying drawing, the projectile there shown comprises a subcaliber core 11 having an ogive nose portion 11a and an axially extending rear hub or fuze plug 12 of reduced diameter which may be integral with the core or suitably secured thereto. An elongated cylindrical bourrelet 13, which may be made of reinforced plastic, light metal, fibre, or the like, is mounted on the body of the core over most of the core length except for the ogive portion. In order to prevent the bourrelet from sliding forwardly over the ogive of the projectile core during handling, there is preferably provided a stop 11b which, as shown in FIG. 1, comprises an annular protuberance of the projectile core immediately in advance of the bourrelet.

The hub 12 has a concial portion 13a, the surface of which flares outwardly from the core base at an angle X (FIG. 1). The conical portion preferably terminates a short distance from the rear end of the hub in a short cylindrical section 13b. A sabot 14 of substantially full caliber diameter and of the same external diameter as the bourrelet receives the hub 12 loosely in an axial concial bore 14a having a taper of angle Y and a minor diameter somewhat larger than the major diameter of the hub, so

as to enable ready mounting and easy release of the sabot. In order to insure proper centering of the sabot and to lend adequate support to the projectile core, there is provided a circular recess 14b centrally disposed in the forward surface of the sabot, the recess being of such size as to receive the core base snugly. The outer front surface area of the sabot bears against the bourrelet. A rotating band 15 of copper or other suitable material is mounted by press-fitting or by other suitable means in annular grooves 15a on the periphery of the sabot.

An important feature of the invention resides in holding the sabot and core in snugly assembled relationship by means of a resilient split annular ring 16, preferably of metal, which fits around the tapered surface of the hub 12. The ring is sprung over the rear of the hub and then is forcibly contracted to a wedging position between the tapered surfaces of the hub and sabot so as to force the sabot and projectile core snugly together. In wedging position, the ring exerts a firm locking action which prevents separation of the sabot and projectile core by minor stresses, such as would be occasioned by rough handling of the projectile.

The tapers of the hub and the sabot, the clearance between the tapered members, and the diameter of the locking ring are such that the ring will wedge after sliding some distance down the cone of the hub. The taper angle Y is substantially greater than taper angle X, preferably to the extent of some 5 to 30. I prefer to keep angle Y within the approximate range of 25 to 50 and to keep angle X in the approximate range from 20 to 45 in magnitude in order to achieve positive locking. It will be understood, however, that considerable departure can be made from the ranges of angles given, depending upon smoothness of surface and the coeflicient of friction of materials used in constructing the split ring, hub, and the sabot. If desired, the tapered surfaces may be fluted for considerations of weight, surface bearing against the ring, or other reasons.

With differential tapering of the sabot and the core, the

ring in being pushed to locking position exerts an appreciable force against the conical surface of the sabot which tends to press the sabot and core tightly together. In looking position, the ring presses against the hub and sabot and by friction and wedging action holds the sabot and projectile core firmly together without slipping.

If desired, the bourrelet 13 may contain longitudinal slots 13a extending from one end of" the bourrelet, as shown in FIG. 4, leaving an uncut portion 13b. The number and length of the slots 13a'are determined by the strength of the material, it being understood that the-slots Weaken the bourrelet so that centrifugal force causes disentegration of the bourrelet when the projectile emerges from the muzzel of the gun. The bourrelet, as shown in FIG. 4, has an internal shoulder 130 which is intended to fit over an annular ridge on the projectile to secure the bourrelet against forward motion with respect to the core.

When the projectile isfired from a gun, the turning band 15 engages the rifling of the gun barrel, and due to the tight fit of the sabot 14 on the core 11, the rotation imparted to the turning band is in turn transmitted by the sabot to the core 11. The projectile undergoes acceleration in the gun barrel and the resilient ring 16 is forced rearwardly off of the hub 12 by setback and/or centrifugal force, leaving the sabot 14 and bourrelet 13 free to slide rearwardly 011 the core under the action of the air pressure on the front of the bourrelet and sabot.

In some embodiments of the invention, such as that shown in FIG. 4, the bourrelet disintegrates radially on leaving the gun muzzle due to the centrifugalforce set up by the high speed rotation of the projectile. ,In such cases, the material for the bourrelet and the length of the slots 13a are chosen so that the bourrelet is strong enough to hold together under moderate stresses and when the projectile is confined in the gun barrel but is weak enough to disintegrate radially when the projectile emerges from the gun muzzle.

If desired, the sabot and the bourrelet may be joined together, as by screws, or may be integral so as to constitute a unitary cup-type sabot designed to slide rearwardly off the core when the projectile leaves the gun barrel.

It is obvious that I have provided a sabot type projectile in which the sabot is positively held on a subcaliber core and is adapted to be released only by forces set up when the projectile is fired from a gun.

2,991,719 r d r e I claim:

1. In a projectile havinga'subcaliber core, a boss projecting rearwardly from said core, the surface of said boss being flared rearwardly, an annular sabot mounted on said core and having a portion extending rearwardly therefrom, the inner surface of said rearwardly extending sabot portion being flared to a degree greater than the flare of said boss, and a resilient ring mounted on said boss and abutting said flared surface of the sabot so as to hold said sabot in place on the core, the ring being movable to release said sabot from the core when the projectile is fired, from the gun.

2. A projectile comprising a subcaliber core, a full caliber bourrelet mounted on said core, a detent on said core to secure said bourrelet against forward movement with respect to said core, an annular sabot mounted on the core and adapted to secure said bourrelet against rearward movement with respect to the core, said sabot having a turning band mounted on its periphery and having a rearwardly flared inner surface extending rearwardly of the core, a boss extending rearwardly from said core, the outer surface of said boss being flared rearwardly to a degree less than the degree of flare of said sabot, a resilient ring mounted on said boss surface and abutting said sabot surface to retain said sabot on said core, said ring being releasable when the projectile is'fired from a gun, to free said sabot and bourrelet for rearward movement from said core.

3. A projectile as described in claim 1 in which the angle made by the flared outer surface of the boss and the axis of the core is in the rangeof 20 to and the angle made by the flared inner surface of the sabot portion with said axis is in the range of 25 to said last named angle being from 5 to 30' greater than said first named angle.

References Cited in the, fileof this patent UNITED STATES PATENTS 217,756 Varney July 22, 1879 1,209,611 Mustin Dec. 19, 1916 FOREIGN PATENTS 131,034 Great Britain Aug. 21, 1919 804,237 France July 27, 1936 

